An in vitro system capable of encapsulating T7 DNA so as to form viable phage particles will be used to monitor the biological activity of DNA replicated or repaired in separate in vitro reactions. The response of the in vitro DNA replication system to exogenous DNA template exposed to potentially mutagenic chemicals will be examined. An effort will be made to detect fixation of mutations during in vitro replication when previously damaged DNA is used as a template and when mutagens are present during th replication reaction. Also the effect of replication by extracts prepared from E. coli mutator strains such as mutator T will be tested. It is hoped that these studies will provide some insight into the biochemistry of mutagenesis and will eventually allow improved understanding of molecular events at the replication fork which affect the fidelity with which the genetic material is duplicated. In another aspect of this study we will examine in vitro repair of DNA damage caused by exposure to alkylating agents and other harmful chemicals. Special attention will be given to error-prone repair pathways. As part of this study we hope to examine UV-reactivation of T7 DNA in vitro and perhaps identify proteins that are induced after exposure of the hot bacteria to sublethal UV damage and improve the survival of irradiated infecting phage. An effort will also be made to examine mutation due to excision repair being performed by extracts of bacteria previously exposed to low doses of ultraviolet radiation.